[RFC PATCH 14/56] x86/bugs: Reset GDS mitigations

David Kaplan
2025-10-13T14:35:37Z

Add function to reset GDS mitigations back to their boot-time defaults.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
---
arch/x86/kernel/cpu/bugs.c | 13 +++++++++++++
1 file changed, 13 insertions(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 112553058ccc..e765ac0b9240 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -1182,6 +1182,18 @@ static void __init gds_apply_mitigation(void)
pr_info("%s\n", gds_strings[gds_mitigation]);
}

+#ifdef CONFIG_DYNAMIC_MITIGATIONS
+static void gds_reset_mitigation(void)
+{
+ /* To cause the MSR bit to be cleared. */
+ gds_mitigation = GDS_MITIGATION_OFF;
+ if (x86_arch_cap_msr & ARCH_CAP_GDS_CTRL)
+ update_gds_msr();
+ gds_mitigation = IS_ENABLED(CONFIG_MITIGATION_GDS) ?
+ GDS_MITIGATION_AUTO : GDS_MITIGATION_OFF;
+}
+#endif
+
static int __init gds_parse_cmdline(char *str)
{
if (!str)
@@ -3941,5 +3953,6 @@ void arch_cpu_reset_mitigations(void)
mmio_reset_mitigation();
srbds_reset_mitigation();
srso_reset_mitigation();
+ gds_reset_mitigation();
}
#endif
--
2.34.1